Selective Zeolite Catalyst for Alkylation of Benzene with Ethylene to Produce Ethylbenzene

Appl Petrochem Res (2012) 2:73–83 DOI 10.1007/s13203-012-0022-6 KACST FORUM Selective zeolite catalyst for alkylation of benzene with ethylene to produce ethylbenzene Mohammed C. Al-Kinany • Hamid A. Al-Megren • Eyad A. Al-Ghilan • Peter P. Edwards • Tiancun Xiao • Ahmad. S. Al-Shammari • Saud A. Al-Drees Received: 4 July 2012 / Accepted: 27 October 2012 Ó The Author(s) 2012. This article is published with open access at Springerlink.com Abstract In this work, a selective catalyst of BXE conversion of BZ appeared to be depending strongly on ALKCAT zeolite has been developed with about 30 % of mole ratio of BZ to E at a given temperature. The study has ZSM-5 balanced with kaolinite, and applied for gas-phase shown that the BXE ALKCAT zeolite is active as a catalyst alkylation of benzene (BZ) with ethylene (E). The catalyst for the alkylation reaction and selective to EB compared has been tested in a fixed-bed down-pass flow reactor under with other zeolite catalysts. different conditions of temperatures ranging between 300 and 450 °C with BZ to E mole ratios ranging between 1:1, Keywords Alkylation Á Ethylation Á Ethylbenzene Á 3:1 and 6:1 under atmospheric pressure and space velocity Zeolite ranges between 0.1 and 150 h-1. The BXE ALKCAT zeolite catalyst has been characterized using: scanning electron microscope, X-ray diffraction, specific surface Introduction area, pore volumes, pore size distributions, X-ray photoelectron spectroscopy, and differential thermal analysis, Ethylbenzene is important in the petrochemical industry as and thermo-gravimetric analyses. Ethylbenzene was the an intermediate in the production of styrene, which in turn main product of alkylation, and diethylbenzene isomers is used for making polystyrene, a common plastic material. (ortho-, meta-, and para-) were the minor products. In the In industry, EB is mainly manufactured by the alkylation of case of 1:1 mol ratio of BZ to E, the selectivity of EB about benzene with ethylene via two methods, i.e., the gas-phase 85.5 % at highest conversion of BZ was obtained after 1 h method [1–5] and the liquid-phase method. The gas-phase of reaction on stream at 450 °C. A decrease in the tem- method is the Mobil–Badger technology, which used perature to 300 °C (with 1:1 mol ratio) caused the selec- mostly molecular sieve catalyst, e.g. ZSM families like tivity of EB to decrease to 73.0 %. EB and DEBs yields ZSM-5 and ZSM-22, because of their unique advantages of were found to increase with increasing the reaction tem- highly selective, less toxic, environmentally friendly and perature and decreasing the mole ratio of BZ to E. The readily reproducible in catalytic reactions [6, 7]. Another reason for ZSM-5 zeolite catalyst being used in alkylation of benzene with ethylene is that its proper pore size can M. C. Al-Kinany Á H. A. Al-Megren (&) Á increase the EB diffusion, while it prevents the polyeth- E. A. Al-Ghilan Á S. A. Al-Drees ylbenzene (PEB) to diffuse through the catalyst [3, 4, 8, 9]. Petrochemicals Research Institute, King Abdulaziz City However, ZSM-5 zeolite has high acid strength and acid for Science and Technology, P.O.Box 6086, Riyadh 11442, amount, which easily catalyses the carbon formation from Saudi Arabia e-mail: [email protected] ethylene [10, 11]. Therefore, in this process, the benzene to ethylene molar ratio is about 8–16 which increases the P. P. Edwards Á T. Xiao Á Ahmad. S. Al-Shammari Á needed energy in the fraction unit for the separation of EB S. A. Al-Drees from benzene and transethylbenzene. Inorganic Chemistry Laboratory, Wolfson Catalysis Centre, KACST-Oxford Petrochemicals Research Centre (KOPRC), In addition, the gas-phase method normally is carried University of Oxford, South Parks Road, Oxford OX1 3QR, UK out under moderate pressure (1.0–20.8 MPa) and high 123 74 Appl Petrochem Res (2012) 2:73–83 temperature (573–773 K), which leads to higher energy Catalyst characterization consumption, more cooling systems and strict requirements for the apparatus. Many years’ industrial operation results X-ray diffraction (XRD) showed that the pure ZSM-5 based catalyst suffers from several disadvantages. For example, more byproducts are Measurements were conducted using Brucker diffracto- produced, especially toluene at about 1,000–2,000 ppm, meter D8 which utilizes Ni-filtered CuKa radiation which is much higher than the levels required by the (k = 1.54 A˚ ). Diffraction patterns were obtained with downstream processes; the selectivity toward ethyl ben- X-Ray gun operated at 40 kV and 30 mA with a scan rate zene is low, and the deactivation of the catalyst is so of 4°/min (2h). serious that it requires periodic regeneration. The byproducts and the rapid deactivation of the ZSM-5 catalyst Scanning electron microscope (SEM) for the alkylation are believed to be due to its strong acidity. The crystal size and morphology of BXE ALKCAT cata- Kaolinite has been widely used as binder and balanced lyst were determined with a FEI–NNL200, 5 kV and work material for zeolite catalyst, because it has global pore with distance 5.0 mm. The silicon and aluminum contents of the 105 A mean pore size, which has little effect on the dif- BXE ALKCAT zeolites were obtained using EDAX fusion of the reactants products [12–14]. It also allows the Ametek-Model 60040, 10 kV. easy process and extrudation of the acid catalyst. In this work, 30 wt% of ZSM-5 catalyst has been mixed with X-ray photoelectron spectroscopy (XPS) kaolinite and tested for benzene alkylation with ethylene at low benzene to ethylene ratio; the results show that the low XPS studies were recorded using JEOL JPS 9010MC content of ZSM-5 zeolite catalyst is suitable for low ben- photoelectron spectrometer, using MgKa (1,253.6 eV) zene to ethylene ratio and high stability. This may be radiation from an X-ray source operating at 10 kV and promising to reduce the cycle and save energy. 20 mA, and the base pressure in the analysis was kept in the range from 5 9 10-10 to 1 9 10-9 mbar. The binding energies (BE) were referenced to the C1s level at 284.9 eV. Experimental A estimated error of ±0.1 eV can be assumed for all measurements. Catalyst preparation The catalyst, BOX ALKCAT has been prepared using Physisorption analysis prilling process The main active component, e.g., ZSM-5 (Si/Al = 25) is mixed with kaolinite at 30:60 and 10 % of Textural properties were determined by nitrogen adsorp- alumina as the binder. These are mixed with a small tion–desorption experiments. The isotherm was measured amount of water to form a slurry. The slurry is shaped into using a Micrometrics ASAP 2010 system. BET surface particles using a prilling machine (36MM, SZCX 160/45, area, pore volume and pore size measurements studies were made in China). The resultant catalyst particles contain carried out using physisorption technique. The adsorption 30 wt% of ZSM-5, which is then dried in static air at for nitrogen was measured at 77 K. Prior to the experi- 450 °C for 5 h to remove the moisture and volatile ments, the samples were degassed under vacuum at 250 °C impurities. for 6 h. The surface area was calculated using the BET method based on adsorption data. The pore size distribution Chemicals and catalysts for mesopore was analyzed from desorption branch of the isotherm by the Parrett–Joyner–Halenda method and the All chemicals were analytical grade; benzene, ethylben- pore size distribution for micropore was analyzed by HK zene (Fluka Chemie 99.5 %), o-diethylbenzenes (Fluka method. Chemie 98.9 %), m-diethylbenzenes (Fluka Chemie 98.9 %), p-diethylbenzenes (Fluka Chemie 98.9 %), 1,3,5- Differential thermal analysis (DTA) and triethylbenzene (Fluka Chemie 98 %) and 1,2,4,5-tetra- thermo-gravimetric analyses (TGA) ethylbenzene (Fluka Chemie 98 %) were used directly without further purification. Ethylene gas (purity DTA and TGA were recorded on Perkin Elmer (DTA-7) [99.95 %) was obtained from M/s. Abdullah Hashim for with thermal analysis controller TAC-7/DX. The catalyst industrial gases. Hexane (Fluka Chemie) was of high grade samples were recovered after reaction and dried under and spectroscopically highly pure (purity [99.98 %). vacuum before being analyzed by TGA. 123 Appl Petrochem Res (2012) 2:73–83 75 Catalyst evaluation mole ratios from 1:1 to 6:1 at each temperature. Blank reactor runs were conducted and no significant conver- The catalytic behavior of BXE ALKCAT zeolite catalyst sions were observed under the conditions of alkylation for the alkylation of benzene with ethylene was studied in a reaction. conventional bench-top pilot plant, as shown in Fig. 1, fitted with a fixed-bed down-flow stainless steel reactor Gas chromatographic analysis with an internal diameter of 5 mm and 35 cm long at atmospheric pressure and temperature ranging between 300 Gas chromatographic analysis of the alkylation products and 450 °C. The reactor was coupled to a mass flow meter was performed on Varian 3800 series instrument fitted with to measure un-reacted ethylene. The reactor was heated in a flame ionization detector and a 50 m 9 0.25 mm glass an electrical furnace, and the reactor’s temperature was open tubular capillary PONA column. The column tem- measured by a thermocouple located inside the furnace and perature was programmed as an initial temperature of was controlled by a temperature controller (Cole-Parmer 30 °C for 15 min, then 60 °C for 20 min (heating rate Digi-sense).

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